Heretofore, for example, there has been known a seat of the type described in JP 2002-306273A. As illustrated in FIG. 5A, this type of seat comprises a seat frame 20, and a stretchable planar elastic body 21 mounted to the seat frame 20 in a tensioned state.
More specifically, the planar elastic body 21 has an end to which respective one ends of an elastic skin 22 and a stay cloth 23 are sewn. The other ends of the elastic skin 22 and the stay cloth 23 are locked to a wire body 25 of the seat frame 20 through a hook member 24 composed of a generally J-shaped synthetic resin body, and intermediate portions of the elastic skin 22 and the stay cloth 23 are wound around the seat frame. In this way, the planar elastic body 21 is mounted to the seat frame 20 in a tensioned state.
There has also been known a seat of the type described in JP 2003-09996A. As illustrated in FIG. 5B, this type of seat comprises a seat frame (main frame) 20, and a planar elastic body (net) 21 provided inside the seat frame 20 in a tensioned state.
More specifically, the planar elastic body 21 has an end to which a selvage cloth 26 is sewn, and a J-shaped hook member (frame hook) 24 is sewn to the selvage cloth 26. Then, the hook member 24 is locked to the seat frame 20, thereby allowing the planar elastic body 21 to be mounted to the seat frame 20 in a tensioned state. Although the JP 2003-09996A does not particularly mention a material of the hook member 24, it may be assumed to be a synthetic resin, because the hook member 24 is attached to the selvage cloth 26 by sewing.
In cases where the above mounting structure of the planar elastic body 21 is employed in a seat cushion, a relatively large load based on a body weight of a seated person who is seated in the seat cushion is applied to the hook member 24 through the planar elastic body 21. On the other hand, in cases where the above mounting structure is employed in a seat back, a relatively large load is also applied to the hook member 24 through the planar elastic body 21 when a seated person leans against the seat back.
When such a large load is applied to the synthetic resin hook member 24, a locking portion of the hook member 24 with respect to the seat frame 20 undergoes flexural deformation, which is likely to lead to a situation where the locking portion is expanded and thereby the hook member 24 is disengaged from the seat frame 20. If the disengagement of the hook member 24 occurs, a support function of the planar elastic body 21 is spoiled, causing, in a seat cushion, a problem that a seated person's hip undesirably sinks downwardly, and, in a seat back, a problem that a seated person's back undesirably sinks rearwardly.